-LRB- ArsTechnica -RRB- -- Even a watered-down version of the law could n't pass muster : San Francisco 's ordinance requiring retail outlets to inform consumers about the -LRB- alleged -RRB- effects of cell phone radiation has been blocked by a federal judge .

Upon passage , San Francisco 's ordinance was challenged by industry trade group CTIA-The Wireless Association , which claimed the ordinance 's requirement that retailers post messages about cell phone safety violated the First Amendment .

San Francisco initially agreed to amend the ordinance after the CTIA filed suit , and made some changes , but they were n't enough . Judge William Alsup found that the ordinance failed the sniff test on both scientific and First Amendment grounds .

`` Whether or not cell phones cause cancer is a debatable question and , at this point in history , is a matter of opinion , not fact . San Francisco has its opinion . The industry has the opposite opinion , '' wrote Judge Alsup .

The fact-sheet required by the ordinance is `` misleading and must be corrected , '' notes the judge . `` Although each factoid in isolation may have an anchor in some article somewhere , the overall message of the fact-sheet -LRB- and the poster , for that matter -RRB- is misleading by omission in two important ways . The overall impression left is that cell phones are dangerous and that they have somehow escaped the regulatory process . ''

The World Health Organization issued a report that seemingly butressed San Francisco 's position in May when it labeled cellphones `` possibly carcinogenic , '' meaning that there is `` limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals . ''

But results of a massive , 15-year-long study released earlier this month showed absolutely no link between cellphone use and cancer , echoing the findings of numerous other studies .

The judge left the door open to the possibility that a revised `` fact sheet '' could pass muster and stayed the enforcement of the law until November 30 so that both sides can file appeals . San Francisco has already promised to do exactly that .

COPYRIGHT 2011 ARSTECHNICA.COM

@highlight

CTIA contests ordinance for consumers to be informed about cell phone radiation hazards

@highlight

Judge William Alsup finds the ordinance failed the sniff test on scientific grounds

@highlight

A 15-year-long study shows no link between cell phone use and cancer